My goal for this career development award is to become an independent researcher specializing in the development and application of statistical methods for behavioral lifestyle interventions. I am a biostatistician with significant experience analyzing data from randomized clinical trials and developing methods for handling missing data. This K07 award will build on this past experience by: (1) providing training in diet and physical activity interventions, focusing on assessment, adherence, and the determinants of lifestyle behaviors, and (2) providing mentored guidance to develop statistical methods specifically designed to analyze real-time diet and activity data that is gathered in clinical trials of behavioral interventions. To achieve these goals, I have developed a comprehensive educational plan, including expert mentors consisting of a behavioral interventionist, a biostatistician who specializes in behavioral interventions, a kinesiologist whose research expertise is in physical activity assessment, a nutritional epidemiologist, and a statistician who is an expert in the analysis of accelerometer output. The research I have proposed both reinforces my training and provides original, innovative statistical methodology to answer important questions regarding behavioral interventions. The research plan focuses on the following specific aims: 1) Develop statistical models to investigate the effects of physical activity on diet at the real-time level. 2) Identify the factors which are predictive of long-term behavior change. 3) Extend the statistical models in aims 1 and 2 by relaxing assumptions regarding missing data. The research and training in this career development award will prepare me to be a principal investigator on research projects and grants that develop statistical methodology to investigate mechanisms of behavior change and improve the assessment of diet and activity behaviors.